/*
 * Copyright 2002-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package qunar.tc.bistoury.instrument.client.spring.el;

import org.objectweb.asm.MethodVisitor;

import java.math.BigDecimal;
import java.math.BigInteger;

/**
 * Implements the {@code multiply} operator.
 *
 * <p>Conversions and promotions are handled as defined in
 * <a href="http://java.sun.com/docs/books/jls/third_edition/html/conversions.html">Section 5.6.2 of the
 * Java Language Specification</a>, with the addiction of {@code BigDecimal}/{@code BigInteger} management:
 *
 * <p>If any of the operands is of a reference type, unboxing conversion (Section 5.1.8)
 * is performed. Then:<br>
 * If either operand is of type {@code BigDecimal}, the other is converted to {@code BigDecimal}.<br>
 * If either operand is of type double, the other is converted to double.<br>
 * Otherwise, if either operand is of type float, the other is converted to float.<br>
 * If either operand is of type {@code BigInteger}, the other is converted to {@code BigInteger}.<br>
 * Otherwise, if either operand is of type long, the other is converted to long.<br>
 * Otherwise, both operands are converted to type int.
 *
 * @author Andy Clement
 * @author Juergen Hoeller
 * @author Sam Brannen
 * @author Giovanni Dall'Oglio Risso
 * @since 3.0
 */
class OpMultiply extends Operator {

    public OpMultiply(int pos, SpelNodeImpl... operands) {
        super("*", pos, operands);
    }


    /**
     * Implements the {@code multiply} operator directly here for certain types
     * of supported operands and otherwise delegates to any registered overloader
     * for types not supported here.
     * <p>Supported operand types:
     * <ul>
     * <li>numbers
     * <li>String and int ('abc' * 2 == 'abcabc')
     * </ul>
     */
    @Override
    public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
        Object leftOperand = getLeftOperand().getValueInternal(state).getValue();
        Object rightOperand = getRightOperand().getValueInternal(state).getValue();

        if (leftOperand instanceof Number && rightOperand instanceof Number) {
            Number leftNumber = (Number) leftOperand;
            Number rightNumber = (Number) rightOperand;

            if (leftNumber instanceof BigDecimal || rightNumber instanceof BigDecimal) {
                BigDecimal leftBigDecimal = NumberUtils.convertNumberToTargetClass(leftNumber, BigDecimal.class);
                BigDecimal rightBigDecimal = NumberUtils.convertNumberToTargetClass(rightNumber, BigDecimal.class);
                return new TypedValue(leftBigDecimal.multiply(rightBigDecimal));
            } else if (leftNumber instanceof Double || rightNumber instanceof Double) {
                this.exitTypeDescriptor = "D";
                return new TypedValue(leftNumber.doubleValue() * rightNumber.doubleValue());
            } else if (leftNumber instanceof Float || rightNumber instanceof Float) {
                this.exitTypeDescriptor = "F";
                return new TypedValue(leftNumber.floatValue() * rightNumber.floatValue());
            } else if (leftNumber instanceof BigInteger || rightNumber instanceof BigInteger) {
                BigInteger leftBigInteger = NumberUtils.convertNumberToTargetClass(leftNumber, BigInteger.class);
                BigInteger rightBigInteger = NumberUtils.convertNumberToTargetClass(rightNumber, BigInteger.class);
                return new TypedValue(leftBigInteger.multiply(rightBigInteger));
            } else if (leftNumber instanceof Long || rightNumber instanceof Long) {
                this.exitTypeDescriptor = "J";
                return new TypedValue(leftNumber.longValue() * rightNumber.longValue());
            } else if (CodeFlow.isIntegerForNumericOp(leftNumber) || CodeFlow.isIntegerForNumericOp(rightNumber)) {
                this.exitTypeDescriptor = "I";
                return new TypedValue(leftNumber.intValue() * rightNumber.intValue());
            } else {
                // Unknown Number subtypes -> best guess is double multiplication
                return new TypedValue(leftNumber.doubleValue() * rightNumber.doubleValue());
            }
        }

        if (leftOperand instanceof String && rightOperand instanceof Integer) {
            int repeats = (Integer) rightOperand;
            StringBuilder result = new StringBuilder();
            for (int i = 0; i < repeats; i++) {
                result.append(leftOperand);
            }
            return new TypedValue(result.toString());
        }

        return state.operate(Operation.MULTIPLY, leftOperand, rightOperand);
    }

    @Override
    public boolean isCompilable() {
        if (!getLeftOperand().isCompilable()) {
            return false;
        }
        if (this.children.length > 1) {
            if (!getRightOperand().isCompilable()) {
                return false;
            }
        }
        return (this.exitTypeDescriptor != null);
    }

    @Override
    public void generateCode(MethodVisitor mv, CodeFlow cf) {
        getLeftOperand().generateCode(mv, cf);
        String leftDesc = getLeftOperand().exitTypeDescriptor;
        CodeFlow.insertNumericUnboxOrPrimitiveTypeCoercion(mv, leftDesc, this.exitTypeDescriptor.charAt(0));
        if (this.children.length > 1) {
            cf.enterCompilationScope();
            getRightOperand().generateCode(mv, cf);
            String rightDesc = getRightOperand().exitTypeDescriptor;
            cf.exitCompilationScope();
            CodeFlow.insertNumericUnboxOrPrimitiveTypeCoercion(mv, rightDesc, this.exitTypeDescriptor.charAt(0));
            switch (this.exitTypeDescriptor.charAt(0)) {
                case 'I':
                    mv.visitInsn(IMUL);
                    break;
                case 'J':
                    mv.visitInsn(LMUL);
                    break;
                case 'F':
                    mv.visitInsn(FMUL);
                    break;
                case 'D':
                    mv.visitInsn(DMUL);
                    break;
                default:
                    throw new IllegalStateException(
                            "Unrecognized exit type descriptor: '" + this.exitTypeDescriptor + "'");
            }
        }
        cf.pushDescriptor(this.exitTypeDescriptor);
    }

}
